To complement their iconic flagship brand, Tanqueray No. 10 gin was first launched in 2000 to appeal specifically to martini drinkers. It has a much heavier, classic juniper scent. It also has the unique character of being one of the few gins made with fresh citrus botanicals including grapefruit, lemon, and lime.
Geoff Kleinman of Drink Spirits has a long and informative comparison between No. 10 and the classic gin summarizing, "Tanqueray London Dry Gin is all about how just a few botanicals can come together around juniper to make a complex and flavorful gin, while Tanqueray No. Ten Gin is about presenting a wider palate of flavors to build on for cocktails."
Tanqueray was first made by Charles Tanqueray in London beginning in 1830. Eventually, WWII destroyed most of the distillery and its remnant were relocated to Scotland, where it is made today. Tanqueray was one of the first distilleries to use double-distillation methods (later, triple-distillation and today quadruple-distilled) as well as being one of the very first "premium" gins on the market. Charles Tanqueray was preceded by Alexander Gordon and his Gordon's gin from as far back as 1769 and a warrant from King George himself in 1925. The two companies were combined to Tanqueray Gordon & Company in 1898.